1. Technical Field of the Invention
This invention relates to pressure vessels used in process operations requiring extreme cleanliness and operated at elevated pressures and temperatures, and in particular to pressure vessel design and shielded closure mechanisms that facilitate easier and cleaner loading and closing of pressure vessels used in automated wafer treatment processes in a production environment.
2. Background Art
There is a general requirement in the semiconductor industry, and in other industries as well such as the medical industry, for conducting processes that require enclosures or pressure vessels that can be loaded with wafers or other objects to be processed, permit the admittance and removal of process fluids or materials necessary to the process after the enclosure is sealed, and be elevated and ranged in pressure and temperature. Some processes are much more critical as to contamination, and require quick and close control of temperature, pressure, and the volume and timing of the introduction of process fluids to the pressure vessel. Add to that the demand for conducting these processes in a production mode, and the growing sophistication of the processes themselves, and it is amply clear that improvements in pressure vessels are needed.
This disclosure relates in particular to pressure vessels used in operations requiring extreme cleanliness and operated at elevated or high pressures up to 10,000 psi (pounds per square inch) or more, and further, to pressure vessel design and isolated lid locking mechanisms that facilitate easier and cleaner loading and locking of pressure vessels used in automated wafer treatment processes in a production environment.
An example of a process to which these criteria apply, there is the manufacture of MEMS (Micro Electro Mechanical Systems) devices where the process agent is carbon dioxide, used in both liquid and supercritical form. Other actual and prospective process agents operated in supercritical phase conditions which require much higher temperature and pressure than does carbon dioxide. Other semiconductor related applications with strict cleanliness requirements, such as photoresist stripping, wafer cleaning, particulate removal, dry resist developing, and material deposition, all suffer from the same pressure vessel deficiencies, which include particle generation upon closing that causes contamination, closure mechanisms that are not suited for quick and automated closing, problems with automatically loading and unloading the vessel, and problems with the integration of the apparatus in a production line.
In many laboratory and production setups currently in use, the pressure vessel is loaded by vertical placement through an open top port of the same or larger diameter of the wafers being processed, and is unloaded by reverse action. The vessel is typically closed by manually bolting or mechanically clamping the process vessel flanges and its cover flanges together around the perimeter to form a pressure seal. This apparatus and methodology is both slow and prone to introducing particulate contamination due to the mechanical interface and constant wearing of mating surfaces. The particulate is generated immediately within the loading and processing environment, and inevitably contaminates the materials being processed to some degree.
These contaminants are of particular concern in the semiconductor industry, as even trace amounts are sufficient to plague product quality and production efficiencies. When these perimeter flange latching mechanisms are semi-automated for faster closure or production purposes, the contamination problem is simply placed in a free-running mode that gets progressively worse if unattended.
There are many examples in prior art. One such example is an autoclave with a quick opening door assembly. It typically consists of a chamber flange, a rotating locking ring and the door flange. The door and vessel are clamped and unclamped by the rotation of the locking ring only. As the ring rotates, surfaces of the mating wedges force the chamber flange tight against the gasket providing a leak proof static seal. Due to the contact of the wedges sliding across each other, particles are generated and debris put into motion that eventually contaminate the process beyond acceptable tolerances.
A further problem with traditional pressure vessels in a production environment is the difficulty in adapting them to the standard wafer handling robots of the semiconductor industry. Complex carriage systems are often necessary for automation of the loading and extracting of materials being processed, involving complex transitions between horizontal and vertical transport of the wafers between processing stations. Newer industry standards anticipate and provide for cluster tool arrangements, where rotary transport systems move wafers between connected wafer processing machines. It is this need and this environment to which the following disclosure is addressed.
It is an object of the invention to provide an inverted pressure vessel system with shielded closure mechanisms for conducting automated industrial processes under elevated pressure and temperatures. To that end, there is disclosed a pressure chamber with an underside loading port, a vertically movable pedestal arranged directly below the pressure chamber for opening and closing the loading port, the top of the pedestal functioning as the floor of the pressure chamber when the pedestal is raised to a closed position and as a loading platform when the pedestal is lowered to an open position.
There is included a motor and vertical drive system for moving the pedestal between open and closed positions, and a pedestal locking system consisting of another motor and lateral drive system for wedge locking the pedestal in a sealing relationship with the pressure chamber so as to define a process volume within which to conduct the processes.
It being another goal to avoid contamination of the processing environment by loosened particles and debris put in motion by the closing and locking systems, there is provided a shield between the loading and unloading area encompassing the pedestal top and pressure chamber, and the pedestal lateral support structure, and vertical drive and closed position locking mechanisms.
It being a further goal to provide for handling processes requiring control of pressure and temperature within the chamber, there is provided an inlet manifold and an outlet manifold communicating with the process volume within the chamber, the manifolds being connectable to a process fluid control source for delivering process fluids under controlled pressure to the process volume and removing byproducts therefrom. There is also provided a heat exchanging platen in the roof of the process volume which is connectible by fluid lines to an external fluid temperature control system, a heat exchanging platen incorporated onto the pedestal and likewise connectible by fluid lines to the external fluid temperature control system, and a thermocouple sensor configured for sensing temperature in the process volume and connectible for communicating with the external fluid temperature control system.
It is yet another goal of the invention to provide for optimal flow and distribution of the process fluids through the central processing cavity of the pressure chamber. To this end, there are provided divergent inflow channels connecting the inlet manifold to the central processing cavity, and convergent outflow channels connecting the cavity to the outlet manifold.
In further support of the goal of reducing contamination of the process, there is a horizontal shelf structure vertically positioned below the top of the pedestal and with a center hole through which the pedestal operates, with lateral support for the pedestal being attached thereto. There is a vertically collapsible bellows, the upper end thereof being attached by an upper bellows flange around the top of the pedestal and the lower end thereof being attached by a lower bellows flange to the perimeter of the hole in the shelf so as to encircle the pedestal and isolate the lateral support structure and drive and lock mechanisms from the loading and processing environment above.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein we have shown and described only a preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by us on carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention.